To amplify the entire signal in this case, the negative part of the original signal is inverted (flipped to positive) before its presented to the power tube(s) responsible for the negative part of the original waveform. I mentioned earlier that an audio waveform consists of both a positive and negative part. Much like a seesaw, pushing and pulling current through the output transformer. To achieve maximum power efficiency, the fixed bias voltage is made extremely negative, down to the point where the tubes can only amplify a positive going signal, also known as biasing near cut-off.
Fixed bias in the power section of a push-pull amplifier, as seen in most if not all bass amps, is used in its own special way.Ī push-pull output stage, also known as class-B or class-AB, is mandatory if a tube power amp is expected to deliver some serious power. This specific output stage will use one tube (or several in parallel) for the up-going part, and another for the down-going part of the original waveform. This article focuses on the power section where the fixed version reigns supreme the grid of the tube is pulled negative, while the cathode is at (or close to) 0 volts. Cathode bias and fixed bias being the most common. This predefined voltage difference between the grid and cathode is called the bias. – make the grid more negative than the cathode (cathode stays at 0 volts, called fixed bias)
– make the cathode more positive than the grid (grid stays at 0 volts, called cathode bias or auto bias) To amplify the entire signal, there are two main options: An audio waveform however consists of both a positive and negative part. More precise, it will only do so for a signal that’s ‘more negative’ relative to the tube’s cathode voltage. What if the amplifier itself would automatically take care of setting the optimum bias and keep it that way no matter what? A deBont bass amp will do just that. No more manual adjustments… ever!Ī tube will amplify the signal presented on its input, called the (control)grid. Regular checkups in between swaps are strongly advised to avoid various issues and maintain a consistent sound. An engineer will manually set the bias voltage when replacing the power tubes. It impacts the tone, proper operation and lifespan of a tube amp’s output section. If you’ve ever owned, regularly used or just love tube amps, then you’re probably familiar with the bias setting.
0 kommentar(er)
